Accurate Measurements of Infinite Dilution Activity Coefficients Using Gas Chromatography with Static-Wall-Coated Open-Tubular Columns

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• 作者：Qianqian Xu ; Baogen Su ; Xinyi Luo ; Huabin Xing ; Zongbi Bao ; Qiwei Yang ; Yiwen Yang ; Qilong Ren
• 刊名：Analytical Chemistry
• 出版年：2012
• 出版时间：November 6, 2012
• 年：2012
• 卷：84
• 期：21
• 页码：9109-9115
• 全文大小：278K
• 年卷期：v.84,no.21(November 6, 2012)
• ISSN：1520-6882

文摘

Wall-coated open-tubular (WCOT) columns provide higher column efficiency and lower solute interfacial adsorption effect than packed columns. However, previous efforts used to measure the infinite dilution activity coefficient (纬^{鈭?/sup>) via a chromatographic technique have used packed columns, because the low carrier gas flow rate (U) and the small stationary phase amount (n₂) in WCOT columns raise large errors. By rationally revising the 纬鈭?/sup>-calculation equation for static-wall-coated open-tubular column, we observed that U and n₂ are not necessarily needed and the resulting error could be reduced, and WCOT column gas chromatography subsequently became a superior method for the accurate 纬鈭?/sup> determination. In this study, we validate our revised 纬鈭?/sup>-calculation equation by measuring 纬鈭?/sup> in an ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate system, in which 55 organic compounds covering a wide range of functional groups were used as probe solutes and their 纬鈭?/sup> values in the ionic liquid were determined at 40.0, 50.0, and 60.0 掳C. Experimental error analysis shows that our revised equation remarkably reduces the error compared to the common 纬鈭?/sup>-calculation equation. Our data is consistent with previously reported values obtained via other techniques, which further proves the credibility of our revised equation. The accurately determined 纬鈭?/sup> values can be directly used to calculate the partial molar excess enthalpy, selectivity, and capacity, which will benefit for the rapid screening of solvents (especially ionic liquids) in separation approaches.}